1. Sep 21, 2004

### dmitridj

Hey, I am having some trouble solving this problem..soon as i see how it works i just know i gunna go "Ooh, thats all i had to do" Here it is:

A shrinking lollipop. A shperical Tootsie Roll Pop that you are enjoying is giving up volume at a steady rate of 0.08 mL/min. How fast will the radius be decreasing when the Tootsie Roll Pop is 20 mm across?

Ok, I know I need to take the derivative of V=(4/3)pi(r^3) i just get lost in that proccess...please help..

THank you very much

2. Sep 21, 2004

### Pyrrhus

They are asking you for $$\frac{dr}{dt}$$

Why don't you differiantiate with respect to t?.

3. Sep 21, 2004

### Pyrrhus

Show me your derivative, so i can see where it went wrong.

4. Sep 21, 2004

### mathwonk

you need to use the chain rule, dV/dt = (dV/dr) (dr/dt)